BBC: Scientists have shown that a severe snowfall in North America and Northern Europe in the winter of 2009-2010 was caused by a rare, once in a century, collision of two weather systems. They concluded the harsh winter and heavy snow was an example of hard to predict weather events, not a change in climate. They analysed historical snow records. The research was published in Geophysical Research Letters. In the winter of 2009-2010 much of Northern Europe experienced …